None.
The invention described herein may be made, used, or licensed by or for the United States Government for Governmental purposes without the payment of any royalties thereon or therefor.
1. Field of the Invention
The present invention relates to a novel formulation for a munitions propellant. In particular, the present invention relates to a munitions propellant comprising:
a nitrocellulose component comprising about fifty-two percent (52.0%) of the munitions propellant by weight, and comprising-a.nitrocellulose composition chosen from the group consisting of:
a nitrocellulose having a nitrogen proportion of twelve and six-tenths percent (12.6%) nitrogen, and
a combination of a nitrocellulose composition having a nitrogen proportion of twelve and six-tenths percent (12.6%) nitrogen and a nitrocellulose composition having a nitrogen proportion of thirteen and thirty-five one hundredths percent (13.35%), said combination having an average nitrogen proportion of thirteen and five one-hundredths percent (13.05%);
a nitroester-based plasticizer component comprising from about thirty-four percent (34.0%) to about thirty-five percent (35.0%) of the munitions propellant by weight, and comprising diethylene glycol dinitrate (DEGDN);
a burning rate temperature coefficient reducing component comprising about seven percent (7.0%) of the munitions propellant by weight, and comprising nitroguanidine (NQ); and,
a non-nitroester-based plasticizer component comprising from about three percent (3.0%) to about four percent (4.0%) of the munitions propellant by weight, and comprising di-normal propyl adipate (DNPA).
2. Description of Related Art
Many energetic compositions are manufactured with, or contain, various compounds that may be hazardous from an environmental point of view, or even toxic. This is particularly true of certain munitions. The current M14 formulation contains toxic and hazardous materials including dinitrotoluene (DNT), dibutylphthalate (DBP), and diphenylamine (DPA). Diphenylamine (DPA) is classified as a highly toxic material, dibutylphthalate (DBP) is a suspected carcinogen, and a Department of Health and Human Services study has linked exposure to dinitrotoluene (DNT) with increased liver, bile duct and gall bladder cancers.
Removing these toxic components from the manufacture of M14 munitions would be a great improvement in the health and safety of the workers preparing such munitions. Another important step would be eliminating the need for solvents in the manufacturing process. This would eliminate many environmental concerns. A new formulation that would permit both the removal of toxic components and eliminate the need for the use of solvents in the manufacturing process would be a great step forward. There has existed a need to address these health and environmental hazards and make both the manufacturing and use of M14 propellant munitions both safer and more environmentally friendly.
At the same time, there are some disadvantages with the current M14 formulation that make it disadvantageous in use, and if these could also be addressed, a new propellant formula would have a distinct IM advantage. One such problem is the susceptibility of the current M14 propellant formulation to a kinetic energy penetrator. The nitrocellulose-based propellants of the prior art met the propellant requirements for M865, M831, and MPAT training rounds that uses the current M14 propellant and have been in use for some time. However, this prior art formulation remains subject to a kinetic energy penetrator, and this has created a greater risk in the event of a training accident.
It is an object of the present invention to provide a propellant formulation that does not employ toxic components.
It is a further object of the present invention to provide a propellant formulation that may be produced without the use of solvents.
It is a still further object of the present invention to provide a propellant formulation that is less sensitive to kinetic energy penetration.
The other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiment thereof.
According to a preferred embodiment of the present invention, there is provided a munitions propellant comprising:
a nitrocellulose component comprising about fifty-two percent (52.0%) of the munitions propellant by weight, and comprising a nitrocellulose composition chosen from the group consisting of:
a nitrocellulose having a nitrogen proportion of twelve and six-tenths percent (12.6%) nitrogen, and
a combination of a nitrocellulose composition having a nitrogen proportion of twelve and six-tenths percent (12.6%) nitrogen and a nitrocellulose composition having a nitrogen proportion of thirteen and thirty-five one hundredths percent (13.35%), said combination having an average nitrogen proportion of thirteen and five one-hundredths percent (13.05%);
a nitroester-based plasticizer component comprising from about thirty-four percent (34.0%) to about thirty-five percent (35.0%) of the munitions propellant by weight, and comprising diethylene glycol dinitrate (DEGDN);
a burning rate temperature coefficient reducing component comprising about seven percent (7.0%) of the munitions propellant by weight, and comprising nitroguanidine (NQ); and,
a non-nitroester-based plasticizer component comprising from about three percent (3.0%) to about four percent (4.0%) of the munitions propellant by weight, and comprising di-normal propyl adipate (DNPA).
The present invention is the result of a program to develop a suitable replacement for the present formulation employed as a propellant in M14 projectiles. To be acceptable as a replacement formulation, however, a new formulation should maintain the performance characteristics of the existing formulation while, eliminating or significantly reducing the problems associated with the current formulation.
Perhaps the most pressing of the problems associated with the current formulation is the use of composition components for which significant health problems have been demonstrated. In this regard, diphenylamine (DPA) is classified as a highly toxic material, dibutylphathalate (DBP) is a suspected carcinogen, and workers exposed to dinitrotoluene (DNT) have been shown to have a 2.5 times greater likelihood to have liver, bile duct, and gall bladder cancers. Increased controls and workplace limitations can be expected on all of these compounds.
In addition, the manufacture of the current M14 formulation, like many energetic compositions, still involves the use of organic solvents. This creates an environmental issue, since environmental regulations increasingly limit the release of organic solvents, and capture of off-gased solvents creates a diseconomy in the manufacturing process. Any reformulation of the propellant material employed in M14 cartridges should address the environmental impact of the reformulated materials.
Finally, as noted previously, the current formulation for M14 propellant meets the current requirements for M14 performance. Typical performance numbers for the prior art M14 formulation are given in Table 1 below, but include a density of 1.594 grams per cubic centimeter (g/cc), a flash temperature of 2757 degrees Kelvin (xc2x0 K.), and an Impetus of 995 joules per gram (J/gm.). There are, however, some characteristics that could be improved. This is particularly true of its kinetic energy penetration characteristics. The nitrocellulose-based propellant formulation currently in use tends to work harden in processing and become brittle. In order to decrease the propellant sensitivity to training round impact, the propellant brittleness must be reduced. In the present invention, this has been accomplished by lowering the nitrogen content of the nitrocellulose and by plasticization of the materials.
In the formulation of Example A, the average nitrogen content of the nitrocellulose has been reduced to thirteen and five one-hundredths percent nitrogen by utilizing a mixture of nitrocellulose sources. This formulation utilizes a mixture of a nitrocellulose with a nitrogen content of thirteen and thirty-five one-hundredths percent (13.35%) and a nitrocellulose with a nitrogen content of twelve and six-tenths percent (12.6%) nitrogen. Along with this nitrocellulose mixture, a nitroester-based energetic plastizer, diethylene glycol dinitrate (DEGDN) and a non-nitroester based plasticizer, di-normal propyl adipate (DNPA), are employed, which results in a propellant which is far less brittle.
The formulation of Example B, goes a bit further in reducing the brittleness of the formulation by employing only a nitrocellulose with a nitrogen level of twelve and six-tenths percent (12.6%) nitrogen. This nitrocellulose is plasticized with diethylene glycol dinitrate (DEGDN) and di-normal propyl adipate (DNPA).
Di-normal propyl adipate (DNPA) was employed, in addition to the nitroester plasticizer diethylene glycol dinitrate (DEGDN), because of its superior performance at low temperatures, and nitroguanidine (NQ) was employed in both formulations to assist in maintaining the low temperature performance coefficients.
Small proportions of additional additives were also employed in the formulations for various purposes. For example, a small amount of wax was added as a processing aid, and graphite was added to the formulations to make the propellant material conductive and therefor safer to handle. Potassium Sulfate was added to reduce muzzle flash in the finished propellant.